This report provides a high-level summary of the understanding of the current state of the climate, including how it is changing and the role of human influence, the state of knowledge about possible climate futures, climate information relevant to regions and sectors, and limiting human-induced climate change.

The report finds that it is unequivocal that human influence has warmed the atmosphere, ocean and land. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred.

Human influence has warmed the climate at a rate that is unprecedented in at least the last 2000 years, where global surface temperature has increased faster since 1970 than in any other 50-year period. Observed warming is driven by emissions from human activities, with greenhouse gas (GHG) warming partly masked by aerosol cooling.

Human-induced climate change is already affecting many weather and climate extremes in every region across the globe. Evidence of observed changes in extremes such as heatwaves, heavy precipitation, droughts, and tropical cyclones, and their attribution to human influence, has strengthened.

This report assesses the climate response to five scenarios that cover the range of possible future development of drivers of climate change. These include scenarios with high and very high GHG emissions that roughly double from current levels, to scenarios with very low and low GHG emissions and CO2 emissions declining to net zero.

Global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered.

With every additional increment of global warming, changes in extremes continue to become larger. This results in the intensity and frequency of hot extremes, heavy precipitation, as well as agricultural and ecological droughts in some regions.

Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.

With further global warming, every region is projected to increasingly experience concurrent and multiple changes in climatic impact-drivers. Changes in several climatic impact-drivers would be more widespread at 2°C compared to 1.5°C global warming and even more widespread and/or pronounced for higher warming levels.

It is expected that regional mean relative sea level rise will continue throughout the 21st century, except in a few regions with substantial geologic land uplift rates.

Cities intensify human-induced warming locally, and further urbanisation together with more frequent hot extremes will increase the severity of heatwaves. Urbanisation also increases mean and heavy precipitation over and/or downwind of cities, extreme rainfall/riverflow events will make flooding more probable.

Limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions.

There is a near-linear relationship between cumulative CO2 emissions and the global warming they cause. This implies that reaching net zero CO2 emissions is a requirement to stabilise human-induced global temperature increase at any level, but that limiting global temperature increase to a specific level would imply limiting cumulative CO2 emissions to within a carbon budget.

1. It is unequivocal that human influence has warmed the atmosphere, ocean and land, at a rate that is unprecedented in at least the last 2000 years. Widespread and rapid changes in the atmosphere, ocean, cryosphere and biosphere have occurred. Each of the last four decades has been successively warmer than any decade that preceded it since 1850.
2. Observed warming is driven by emissions from human activities. Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years. In 2011–2020, annual average Arctic sea ice area reached its lowest level since at least 1850. Global mean sea level has risen faster since 1900 than over any preceding century in at least the last 3000 years.
3. Human-induced climate change is already affecting many weather and climate extremes in every region across the globe, with human influence contributing to many observed changes in weather and climate extremes.
4. Global surface temperature will continue to increase until at least the mid-century under all emissions scenarios considered. Global warming of 1.5°C and 2°C will be exceeded during the 21st century unless deep reductions in CO2 and other greenhouse gas emissions occur in the coming decades.
5. Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level. The climate system is susceptible to being pushed beyond a tipping point, which is a critical threshold beyond which each system reorganizes, often abruptly and/or irreversibly.
6. With every additional increment of global warming, changes in extremes continue to become larger. For example, every additional 0.5°C of global warming causes clearly discernible increases in the intensity and frequency of hot extremes, including heatwaves, and heavy precipitation, as well as agricultural and ecological droughts in some regions.
7. Limiting human-induced global warming to a specific level requires limiting cumulative CO2 emissions, reaching at least net zero CO2 emissions, along with strong reductions in other greenhouse gas emissions. This can only be achieved with a concerted effort between all countries to transform their societies into resilient, zero-carbon economies. This requires significant investments in renewable energy technology, and other initiatives to support a zero-carbon world.